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under 75F and no AC, Prius only got 41 MPG

Discussion in 'Gen 2 Prius Fuel Economy' started by prius-I-like-you, Sep 22, 2012.

  1. prius-I-like-you

    prius-I-like-you New Member

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    ....... I read more and more report, they say prius can got 50 MPG in 70F ~75F. why I can not got this MPG ( only 41 MPG )?

    I know they overfill gas in my car. Is this reason let my prius got low MPG in summer ?
     
  2. richard schumacher

    richard schumacher shortbus driver

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    There are many possible simple causes: the driver has not yet learned the correct behaviours; tire pressure is too low; oil level wrong; nothing but short trips (less than about 10 km); 12V battery failing.

    Who are "they" and why are they overfilling the gas tank?
     
  3. bisco

    bisco cookie crumbler

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    how long have you owned it? how many miles on her? how are you measuring mpg's? wher do you live and what is the terrain like? how is your driving style?
     
  4. prius-I-like-you

    prius-I-like-you New Member

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    total 76000 mile on my prius. I live near new york city and terrain like plain. My driving style is normal ( no rush, no hard push gas )
     
  5. prius-I-like-you

    prius-I-like-you New Member

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    tire pressure is good , Front 35/33. oil level is good.

    12v battery maybe not failing, but I use prius self check , 12v battery only got 11.4v when I drive on road(speed 10~20 mph) .
     
  6. jdenenberg

    jdenenberg EE Professor

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    Your PSI is a bit low as I find that 42/40 gives better MPG.

    What brand/model tires are on your Prius? If you have tires with a high rolling resistance, your MPG will suffer.

    Do you make a lot of short driving trips? That not only lowers MPG as your Prius never warms up, but also leads to never fully charging up the 12v battery.

    The 12v battery in "Ready" mode should be about 14v as the battery is being charged. A voltage of 11.4 in ACC mode (with only a small current drain) is low. What does the battery voltage drop to with the headlights on?

    JeffD
     
  7. cwerdna

    cwerdna Senior Member

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    They who?

    Please answer the questions at Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat.

    Agreed that tire pressure is low.

    Please run the test at Weird stuff happening? MPGs dropping? Test The Battery | PriusChat after the car has sat overnight. Please tell us the values at each step. You should be providing us w/3 values.
     
  8. prius-I-like-you

    prius-I-like-you New Member

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    I will check tires in tomorrow . and I keep watch 12v battery, I drive on street and the battery voltage will drop to 11.4v ( I mean my prius is IG mode ready & running in road ).
     
  9. jdenenberg

    jdenenberg EE Professor

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    A low voltage in ready mode is a bad sign. either the charging system (inverter) or the 12v battery has a shorted cell and is pulling a lot of current.

    JeffD
     
  10. prius-I-like-you

    prius-I-like-you New Member

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    but only turn on IG mode ready, & prius don't move & stop in street. battery go back to 14v.
     
  11. prius-I-like-you

    prius-I-like-you New Member

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    which battery will be match my 2005 prius ? Optima Batteries YellowTop Battery ? or other cheap one ?
     
  12. jdenenberg

    jdenenberg EE Professor

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    So something else is drawing a lot of 12v current when you are moving or your inverter is intermittent. You need to get your Prius to a good hybrid repair facility.

    JeffD
     
  13. jdenenberg

    jdenenberg EE Professor

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    The direct replacement Optima Yellow-Top is model DS46B24R which is the one that I installed in my 2004 Prius.

    JeffD
     
  14. bisco

    bisco cookie crumbler

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    optima is a good choice. get the model for your year with correct battery posts for connections.